What killed thedinosaurs? According to a recent breakthrough study, not a giant meteor impact.
Well, at least not the impact itself. Although the 10km wide Chicxulub asteroid exploded into Earth with more energy than a billion nuclear bombs put together, it was the dust the collision kicked up into Earth’s atmosphere that triggered the dinosaur’s demise 66 million years ago.
That’s according to a new study, published in the journalNature, which suggests it wasfine silicate dust produced by pulverised rock that sparked a dramatic period of global cooling.
“The explosion wasn’t really what doomed the dinosaurs and all the other species that died,” palaeontologistProf Stephen Brusatte, who was not involved, explained toBBC科学重点.
“The dust and soot that went up into the atmosphere put the Earth into a deep chill, and blocked outthe Sunfor at least a couple of years, and with plants unable to photosynthesise, ecosystems would have collapsed like houses of cards. It was probably these tiniest dust particles that had one of the greatest killing effects on life.”
It was previously thought that sulphur released from Chicxulub’s impact, and the soot created from post-impact wildfires, were the main drivers of Earth’s drastic cooling. However, various climate simulations used by a team of scientists from the Royal Observatory of Belgium indicate fine dust played a key role.
When examining rock materials from Tanis – a well-preserved fossil site in North Dakota, US, well-known for providing direct evidence of the Chicxulub impact – the scientists found a much higher distribution of fine silicate debris less than 8 micrometres (0.000008m) across than expected.
Using data from the site, the researchers estimate the dust could have remained in Earth’s atmosphere for 15 years after the asteroid impact, contributing to a 15°C drop in surface temperature.
According to the new simulations, dust – alongside soot and sulphur – would have blocked plants from photosynthesising for two years, as well as triggering a chain reaction of animal extinctions.
In total, the dinosaurs roamed Earth for approximately 165 million years (in comparison,Homo sapienshave only existed for 300,000 years). The Chicxulub asteroid and its aftereffects killed off an estimated 75 per cent of life forms on the planet, including nearly all non-flying dinosaurs and large mammals.
After the mass extinction, life continued in the form of small avian dinosaurs and mammals, many of which would eventually evolve into Earth’s current life forms.
About our expert
Steve Brusatte is a professor of palaeontology at the University of Edinburgh who specialises in the anatomy, genealogy, and evolution of dinosaurs. He served as the dinosaur consultant in the filmJurassic World:Dominion以及BBCWalking with Dinosaurs. His research has been published in journals includingNature,Ecology and Evolution, andCurrent Biology.
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